Question

Python

Write a program that loops, prompting the user for their full name, their exam result (an integer between 1 and 100), and then writes that data out to file called ‘customers.txt’. The program should check inputs for validity according to the following rules:

• First and last names must use only alphabetical characters. No spaces, hyphens or special characters. Names must be less than 20 characters long.
• Exam result (an integer between 1 and 100 inclusive)

The file should record each customers information on a single line and the output file should have the following appearance.

Nurke Fred 58

Cranium Richard 97

Write a second program that opens the ‘customers.txt’ file for reading and then reads each record, splitting it into its component fields and checking each field for validity.

The rules for validity are as in your first program, with the addition of a rule that specifies that each record must contain exactly 3 fields.

Your program should print out each valid record it reads.

The program should be able to raise an exception on invalid input, print out an error message with the line and what the error was, and continue running properly on the next line(s).

Answer 1

1.

'''

Python version : 2.7

Python program to input the firstname, lastname and exam result of customers and output to file customers.txt

'''

# input of number of data to input

n = int(raw_input('Enter the number of records to input : '))

# open file in write mode

file = open('customers.txt','w')

i=0

# loop to input n customer data

while (i < n):

               print('Enter details for customer %d ' %(i+1))

               # input firstname

               fname = raw_input('Enter first name : ')

               # validate first name

               if(fname.isalpha() and len(fname) <= 20):

                              # input last name

                              lname = raw_input('Enter last name : ')

                              # validate last name

                              if(lname.isalpha() and len(lname) <= 20):

                                            

                                             try:

                                                            # input exam result

                                                            result = int(raw_input('Exam result (an integer between 1 and 100 inclusive) : '))

                                                           

                                                            # validate exam result's range

                                                            if(result > 0 and result <=100):

                                                                           # if all valid values write to file

                                                                           if(i == 0):

                                                                                          file.write(lname+' '+fname+' '+str(result))

                                                                           else:

                                                                                          file.write('\n'+lname+' '+fname+' '+str(result))

                                                                           i = i + 1

                                                            # invalid exam result

                                                            else:

                                                                           print('Value of result : '+str(result) +' is invalid')

                                             except ValueError as e: # invalid exam result

                                                            print('Value of result : '+str(e)+' is invalid')

                              else: # invalid last name

                                             print('Value of last name : '+lname +' is invalid')

               else: # invalid first name

                              print('Value of first name : '+fname +' is invalid')

#close the file

file.close()                         

              

#end of program             

Code Screenshot:

Output:

File:

2.

'''

Python version : 2.7

Python program to read firstname , lastname and exam result from customers.txt and validate the fields

and output valid customers and for invalid customers ,

output the reason for the record being invalid and the customer data

'''

# open the input file

file = open('customers.txt','r')

# read a line from file

line = file.readline()

# read till end of file

while(line):

              

               try:

                              # split the data read from file using space as the delimiter

                              # and strip is used to remove any trailing or leading whitespace present in line

                              data = line.strip().split()

                              # validate the number of fields read

                              if(len(data) == 3):

                                             # validate lastname

                                             if(data[0].isalpha() and len(data[0]) <= 20):

                                                            # validate firstname

                                                            if(data[1].isalpha() and len(data[1]) <= 20):

                                                                           result = int(data[2])

                                                                           # validate exam result

                                                                           if result > 0 and result <=100:

                                                                                          print(line.strip())

                                                                           else:

                                                                                          raise ValueError('Value of result : '+str(result)+' is invalid')

                                                            else:

                                                                           raise ValueError('Value of first name : '+data[1]+' is invalid')

                                             else:

                                                            raise ValueError('Value of last name : '+data[0]+' is invalid')

                              else:

                                             raise ValueError('There should be exactly 3 fields')

                              line = file.readline()

               except ValueError as e:

                              print(e)

                              print(line)

#close the file                   

file.close()                         

#end of program                                           

Code Screenshot:

Output:

Input file:

Output: